Available Static Pressure Calculator
Available static pressure for duct design.
Enter your values
Enter the blower total external static in in wc.
Enter the coil pressure drop in in wc.
Enter the filter pressure drop in in wc.
Enter the other fixed losses in in wc.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Available static for ductwork
- 0.2 in wc
- Total fixed losses
- 0.3 in wc
- Status
- OK — proceed to friction rate calc
Quick answer
Available static pressure equals the blower's total external static rating minus the pressure drops of the coil, filter and other fixed components.
Available SP = total external SP - component losses
At a glance
| What it does | Available static pressure for duct design. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Blower total external static, Coil pressure drop, Filter pressure drop, Other fixed losses |
| Main output | Available static for ductwork |
| Formula | Available SP = total external SP - component losses |
| Cost | Free — no sign-up, no download |
How to use the Available Static Pressure Calculator
- 1Find the blower's rated total external static pressure (TESP) from the equipment spec sheet.
- 2Subtract the coil, filter and any other fixed component losses at design airflow.
- 3Use the remaining available static pressure to calculate the design friction rate for the ducts.
Inputs explained
- Blower total external static(in wc)
- Enter the blower total external static in in wc.
- Coil pressure drop(in wc)
- Enter the coil pressure drop in in wc.
- Filter pressure drop(in wc)
- Enter the filter pressure drop in in wc.
- Other fixed losses(in wc)
- Enter the other fixed losses in in wc.
Worked example
Using the values the calculator loads with:
Inputs
- Blower total external static0.5 in wc
- Coil pressure drop0.15 in wc
- Filter pressure drop0.1 in wc
- Other fixed losses0.05 in wc
Results
- Available static for ductwork0.2 in wc
- Total fixed losses0.3 in wc
- StatusOK — proceed to friction rate calc
Frequently asked questions
What if available static is negative?
The fixed components already exceed the blower's capacity — a lower-pressure-drop filter or larger coil is needed before duct design can proceed.
Typical TESP for residential systems?
Often 0.5 in wc, though high-efficiency variable-speed blowers can be rated higher.
What do I need to enter into the Available Static Pressure Calculator?
Just 4 values: blower total external static, coil pressure drop, filter pressure drop, other fixed losses. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Available Static Pressure Calculator work out the answer?
Available static pressure equals the blower's total external static rating minus the pressure drops of the coil, filter and other fixed components. It applies the formula Available SP = total external SP - component losses and shows the working so you can check each step by hand.
Is the Available Static Pressure Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.